I can think of three possible ways (not exhaustive) that a wiki can be used for the area of Language Arts.

1. This can be a place where you track reading (holiday or term time) assignments. As the students do their own readings, they can be asked to answer questions pertaining to the portion of the book they have read, how that particular portion relates to the book as a whole, or even what are some of the implications for modern day applications.

2. This can also be a place where they post their reading journals and thoughts. Some might want to call it blog. Call it what you want but essentially, it is a way for students to post their thoughts and get feedback from both the teacher and fellow classmates.

3. This can also be a place where a collaborative portrait of a character can be painted, the major plots of a story can be formed, or whatever creative elements you would like to carry out in which a collaborative approcah (synchronous or asynchronous) would be helpful.

I have created a sample template of what this might look like,